Magnifying spectacle-glass.



V l w w V J d SEARCH Roo M. voN RoHR. www MAGNIFYING SPECTACLE GLASS.

APELIOATIOI FILED AUG. 25, 1910.

Patented Aug. s, 1911",V

1 ...MSEAEEBO 0 M- UNITED STATES PATENT OFFICE.

MORITZ von ROHR, OF JENA, GERMANY, AssIGNOR To THE FIRM OE CARL zEIss, OF

l JENA, GERMANY.

MAGNIEYING sEoTAoLE-GLASS.

Specification of Letters Patent.

Patented Aug. 8, 1911.

To all whom it may concern:

Be it known that I, MORITZ VON ROHR, a citizen of the German Empire, residing at Carl-Zeiss strasse, Jena, in the Grand Duchy of Saxe-Weimar, Germany, have invented a new and useful Magnifying Spectacle-Glass, of which the following is a specification.

Magnifying spectacle glasses, which are made up like a Galilean telescope of a collective lens and di's'sive lens fitted behind each other with an intervening space (air lens), have frequently been suggested for very short sighted eyes. The constructive forms of such glasses, indicated in such suggestions would, however, as their investigation by calculation has shown, have only a small useful field of vision (if in order to save weight single lenses were used), as the astigmatism along the oblique principal rays increases exceedingly rapidly toward the margin. From the researches which followed this investigation the present invention has resulted, in consequence of which, by giving the lenses a special form, a satisfactory astigmatic correction is attained.

The invention can be regarded as an improvement on such well-known spectacle glasses of the specified combination, the front surface of the collective lens of which has the stronger curvature, so that the collective effect is realized mainly by this front surface, and the air lens of which acts dispersively. The dispersive effect must then be assigned chiefly, for the purpose of the astigmatic correction, to the hinder surface of the dispersive lens, which surface must therefore be more strongly curved than the front surface. The adoption of this means of correction does not interfere with the removal of distortion and also permits of a considerable restriction of the chromatic aberration, which ordinarily has a prejudicial effect in the case of strong spectacles, at least at the margin of the field of vision. In addition to this, such combinations of lenses after the type of the Galilean telescope exhibit the well-known advantageous property, to give magnified images on the retina. When the short sighted eye is astigmatic as well, one of the lens surfaces may be made cylindrical or toric.

-In the annexed drawing: Figure 1 is a diagrammatic view of a spectacle glass constructed according to the invention, by which an exceedingly shortsighted eye is made capable of seeing distant objects sharply. Fig. 2 is a diagrammatic View of the reading glass to be prescribed for the same eye.

For both glasses not only is the astigmatism along the principal rays, which pass through the margin, as good as eliminated, but also the chromatic aberration of the same principal rays is much less than with the simple dispersive spectacle glasses of high power, and further only a small amount of distortion remains.

First example, Fig. 1.-This is a spectacle glass built up of two separate lenses I and II for an eye of 18.dptr. (dioptries) and a very great distance s of the object from the front vertex of the lens I. The section Z2 of the axis between the two lenses is 10.5 mm. long, the section l from the lens II to the point of intersection O of the principal rays (point of rotation of the eye) is 25 mm. The angle of inclination w of the principal rays on the obj ect side amounts for t-he margin of the glass to 10.960", the corresponding angle w on the eye side to 12.0. The magnification of the image on the retina in the direction of the axis is 1.7. The distortion corresponding to the said principal rays is so far eliminated, that the distance of the marginal image points from the axis deviates only by 0.3 per cent. from that one, which would correspond to the magnification existing in the axis. The following table contains, besides the dimensions of the lenses and the kinds of glass, also particulars relative to what remains of astigmatism and chromatic aberration. The astigmatism is represented by the intersectional distances s', and s. (measured on the eye side from the place of emergenceon the hindermost lens surface to the point O) of the sagittal and meridional pencils, which belong to the principal ray coinciding with the axis, to one of mean inclination and to the marginal principal ray. The chromatic aberration is characterized by the angles of inclination we and w1.- of the red and the blue components, which correspond on the object side to the marginal i L f.'

principal ra having on the eye side the angle of inclination w.

Dimensions of the Lenses in mm.

Lens I: zii-5.2 DI=25.0 r1=19u60 r2=8 Lenen: (Ln-0.5 olf-11.5 3=sao1 r.=15.10

Kinds of Glass.

Lens I: nD=1.5164 v=64.1 LensII: nD=L6211 11:36.56

Correction of the Astigmatism.

1u -0 7.751 10. 960 s.=55. 03 mm. 54. O7 mm. 53. 48 mm. s.=55.08 52.80 54.13

Correction of the Chromatio Aberration.

w= 12. 0 1C-10. 973 wF=1o. 947

Second example, Fig. 2.-The defect of the eye again amounts to 18 dptr., but the distance s of the object, which is plane and perpendicular to the aXis of the spectacle glass7 is only 300 mm. The distance b is 10.0 and the distance Z again 25 mm. The greatest angle of inclination w of the principal rays on the object side is 14.3930, the one fw on the eye side is 15.0. The magnilication of the image on the retina in the direction of the axis is 1.7. The distortion at the margin of the image field amounts to 0.6 per cent. The chromatic aberration is defined below, instead of as in the former example by the angles wc and wp, by the distances kc and hp, in which the red and the blue components pierce the object plane.

Dimensions of the Lenses in man. Lens I: dI=4.5 DI=26.6 ipa/.72 r1=479-s Lens II: du=0.5 Dn=14.0 r3=80.98 r,=19.47

Kinds of Glass. Lens I: nD=1.5188 v=60.5 LeusII: nD=1.6211 v=36.2

Correction of the Astigmatsin.

'w =0 10.196 14.393" s.=155. 60 mm. 55. 65 mm. 55. 82 mm. s=55.60 55.24 55.72

Correction of the Chroniatic Aberration.

w=15.0 I1.C=91.06mm. )1FL-91.34 mm.

I claim: Almagnifying spectacle glass forumyo es consisting ot a chromatically non-corrected collective front lens having its front surface this lens.

MORITZ VON ROI-IR. lVitnesses:

PAUL KRGER, ALFRED MACKEDENY.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

, Washington, D. C. 

